One of the more important unwritten rules in rap is to have a great opening line. The likes of Prodigy of Mobb Deep, Biggie, The Clipse, Andre 3000 all have memorable opening lines that are recited to this day. Fashawn out of Fresno, California delivers one of the best opening lines you'll hear in the AM. This is from his 2010 "Grizzly City 3" mixtape and is a personal favourite of mine.
"Woke up, pissed off, dick hard, breath stinkin', just thinkin'
What the fuck am I gonna do with these Abe Lincolns?"